Methods for Increased Accuracy in Numerical Reservoir Simulators

The use of 2-point upstream weighting of fluid mobility is proposed as an alternative to the generally employed single-point approximation. Use of the 2-point formula results in the reduction of both numerical dispersion of flood fronts and the sensitivity of predicted areal displacement performance to grid orientation. Stability analysis provides the time step limitation for control of solution oscillations. This, together with limitations for control of overshoot and truncation error, provides a practical basis for the automatic selection of time steps. (18 refs.)